[DO NOT MERGE] Update security string to 2018-03-01 for mnc-dev Bug:71860241 am: fa4234e1df
am: a615903311

Change-Id: I93a3d87c3410fbf38ce60a6c8d56570c8d75fe9e
diff --git a/core/version_defaults.mk b/core/version_defaults.mk
index c44c1da..21852e2 100644
--- a/core/version_defaults.mk
+++ b/core/version_defaults.mk
@@ -105,7 +105,7 @@
   #  It must match one of the Android Security Patch Level strings of the Public Security Bulletins.
   #
   #  If there is no $PLATFORM_SECURITY_PATCH set, keep it empty.
-  PLATFORM_SECURITY_PATCH := 2018-02-01
+  PLATFORM_SECURITY_PATCH := 2018-03-01
 endif
 
 ifeq "" "$(PLATFORM_BASE_OS)"